It sounds like things are progressing well. The engine is more reliable, you had some able-bodied helpers (at least for part of it), and the owner is learning to sail.

Things to work on:
Find a way to elevate the helm station just a few more inches. That way, the owner can drive at all times, while you pull the strings or handle the foredeck while docking.

Maybe there's a way to adjust the throttle linkage so that you can't kill the engine by throttling down to "zero". Or maybe the idle needs to be adjusted on the engine. If the owner has the "magic touch" to start the engine, figure out what he's doing, that you aren't.

Once he really gets the feeling of the helm pinned down, and becomes a good driver, you guys will make a good team.